This paper describes a lab-on-a-chip device for continuous liquid/solid chromatography measurements. Chromatographic separations of phenolic test solutions as well as of vitamins are illustrating the ability and versatility of the system. The dependence of the peak height and width with respect to the injected plug and the saturation limits of the microchip column have been investigated and good correlation to the theoretical predictions have been observed.The focus of the system design is on simplification of both fabrication complexity and application. To this end, large bore flow-through fluid introduction channels have been integrated onto the chip to allow aliquoting from meso-scale flows of sample (up to tens of milliliters per minute). Repeatable plug injections and reproducible chromatographic separations were achieved in an open-tubular on-chip microcolumn with C 8 stationary phase coating. The entire system allows for a rapid cycle time for multiple analyses, exchange of analyte and mobile phase in less than a minute, and complete cleaning cycles within a few seconds only. This makes it a suitable candidate for on-line process analysis applications.

We present a channel geometry that allows for clean switching between different inlets of a microchip without any contamination of the inlets or the downstream flow. We drive this virtual valve with a pneumatic pressure setup that minimizes disturbance of the downstream flow during the switching procedure by simultaneous variation of the pressures applied to the different inlets. We assess the efficiency of the setup by spectroscopic measurement of downstream dye concentrations, and demonstrate its practical utility by sequentially constructing multiple layers of alginate hydrogel. The method is potentially useful for a whole series of further applications, such as changing perfusion liquids for cell culture and cell analysis, metering, chemical-reaction initiation and multi-sample chromatography, to name a few.

Background/AimsThis study assessed the feasibility of a novel contact lens device for intraocular pressure (IOP) and ocular pulse amplitude (OPA) continuous measurements over 24 hours.MethodsThis prospective, open-label, single-centre, non-randomised study included glaucoma and healthy subjects. IOP and OPA values acquired by the pressure-measuring contact lens (PMCL) device in one patient’s eye at the beginning of the measurement were compared with tonometry values (Goldman applanation tonometry (GAT) and dynamic contour tonometry (DCT)) in the same eye just before PMCL placement. Furthermore, IOP and OPA values measured with PMCL on the study eye during a water drinking test (WDT) were compared with DCT values in the fellow eye. Comparisons were performed using t-tests with 95% Confidence Intervals.ResultsTwenty-four-hour IOP and OPA curves were obtained for eight subjects. The mean IOP difference between PMCL and tonometry on the same eye was within ±5 mm Hg in 75% (GAT) and 87.5% (DCT) of subjects. IOP variations due to WDT were detected by PMCL and DCT, showing an average increase of 2.43 and 1.85 mm Hg, respectively. Differences between PMCL and DCT for IOP variations in fellow eyes were within ±5 mm Hg for 97.2% of time points. The difference between OPA in fellow eyes was within ±5 mm Hg for 85.5% of the time points.ConclusionsThis first-in-human study is a proof-of-concept for 24-hour continuous measurements of IOP and OPA with the PMCL. This device is non-invasive and has good comparability with standard tonometry.

We report on the fabrication of the first MEMS micropump including an integrated pressure sensor. The signal of this sensor allows direct insight into the pump's operating dynamics and enables real-time self-monitoring. We demonstrate the changes in the sensor signal under different pumping conditions, including the presence of air in the pumping chamber and a downstream occlusions. Deviations from normal operating conditions create clear and characteristic deviations from the normal signal. These deviations will be exploited to detect extraordinary or faulty pumping conditions during use.

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